Madhulika Srivastava

Synthesis of novel fused heterocycle-oxa-aza-phenanthrene and anthracene derivatives via sequential one-pot synthesis in aqueous micellar system

Oxa-aza-phenanthrene and anthracene derivatives which contain a bridgehead nitrogen are synthesized in an aqueous micellar system. The synthetic route is easy and yield is excellent. In this proposed method, solvent, base and surfactant are optimized and the best result was obtained by DBU in water with surfactant CTAB. All synthesized molecules are new. This method is an efficient, viable and sequential one pot synthetic route for the construction of desired product.

An environmentally friendlier approach—ionic liquid catalysed, water promoted and grinding induced synthesis of highly functionalised pyrazole derivatives

Grinding induced synthesis of highly functionalised pyrazoles derivatives by use of malanonitrile, phenyl hydrazine and diversified aldehyde. Ionic liquid is used as a catalyst with water, and no by-products form. A high yield is obtained and simple handling are the benefits of the adopted route, and this route fulfils all shades of green chemistry.

Efficient iodine-catalyzed one pot synthesis of highly functionalised pyrazoles in water

An efficient one pot multi-component sequential reaction of phenyl hydrazine, malanonitrile and a diverse range of aldehydes to afford highly functionalised pyrazoles is reported. The reaction proceeds in water using molecular iodine as a catalyst, with no by-product formation, and involves simple operation requiring no column chromatography. Thus, this protocol fulfils all of the criteria that define green chemistry.

A new eco-friendly strategy for the synthesis of novel antimicrobial spiro-oxindole derivatives via supramolecular catalysis

Novel spiro-oxindole derivatives were synthesised by one-pot multicomponent reaction using isatins, urea and 1,3-dicarbonyls. β-Cyclodextrin, an oligosaccharide, catalysed the reaction and can be reused for further reaction after recovery. This developed synthetic route is environmentally benign in which water is used as solvent to produce excellent yields of products. The synthesised compounds were evaluated for their antimicrobial activities against two bacteria and two fungi. All the synthesised spiro-oxindoles exhibit significant antimicrobial activity.

Visible light induced, catalyst free, convenient synthesis of chromene nucleus and its derivatives using water–ethanol mixture as a solvent

A highly efficient, green, eco-friendly, one pot protocol has been demonstrated for the synthesis of 2-imino-2H-chromene-3-carbonitrile (3), 2-aminochromene (4) and chromeno(2,3-b)pyridines (5). The synthesis of the chromene nucleus has been carried out under visible light irradiation in a water–ethanol mixture at room temperature using salicylaldehyde and malononitrile in different proportions. The adopted method shows significant advantages such as mild and clean reaction conditions, eco-friendly procedures, absence of catalysts and a short reaction time. This protocol involves the use of CFL as the visible light source and shows high selectivity in the presence of a mixture of ethanol and water. The reaction proceeds with good to excellent yield.

Visible light triggered, catalyst free approach for the synthesis of thiazoles and imidazo[2,1-b]thiazoles in EtOH : H2O green medium

The development of a visible light promoted, mild and greener approach for the synthesis of highly functionalized thiazoles and imidazo[2,1-b]thiazoles under photochemical activation in EtOH : H2O green medium is demonstrated. The characteristic feature of the present protocol is the utilization of visible light (an omnipresent, nontoxic, environmentally benign and inexpensive reagent) to form C–S and C–N bonds and circumvent the use of catalysts or photosensitizers. The reported protocol is the first example of visible light promoted synthesis of thiazoles and imidazo[2,1-b]thiazoles with various attractive features like being catalyst free, eco-efficient and possessing cost effectiveness, short reaction time, excellent yields and sustainability to fulfill the parameters of green chemistry.

Chitosan/ionic liquid forms a renewable and reusable catalyst system used for the synthesis of highly functionalized spiro derivatives

Chitosan, a reusable heterogeneous catalyst, can be combined with an ionic liquid as a green solvent to generate a highly efficient catalyst system for our densely functionalised and diversified target molecule. The reaction is completed with a good to excellent yield. This procedure demonstrates an eco-friendly catalyst system and eliminates the use of toxic transition metal catalysts, bases and volatile organic solvents, which adversely affect the environment and human beings.

Molecular iodine: a green and inclusive catalyst for the synthesis of highly functionalized 1,3,5-trisubstituted pyrazoles in aqueous medium

A library of 1,3,5-trisubstituted pyrazoles was synthesized in excellent yields from the reaction of aldehyde, phenylhydrazine and alkynes in the presence of iodine via an eco-friendly, simple process performed in aqueous medium. This single pot transformation generates new CN, C–C, C–N bonds and proceeds by a domino reaction involving the formation of Schiff base, Mannich addition and finally intramolecular cyclisation.

Oxidative organophotoredox catalysis: a regioselective synthesis of 2-nitro substituted imidazopyridines and 3-substituted indoles, initiated by visible light

We have established a mild, metal-free, one pot, visible light-catalyzed procedure for a highly regioselective synthesis of 2-nitro-3-arylimidazo [1,2-a] pyridines via nitroalkene and 2-aminopyridine under an open atmosphere involving a photoredox catalyst, Eosin Y, which is an inexpensive organic dye that has been employed as a photo sensitizer in the conversion. This protocol serves as an example of green chemistry, due to the fact that molecular oxygen and visible light have been utilized effectively for the transformation. The procedure involves intramolecular C–N heterocyclization, followed by aerobic oxidation and C–C bond formation at room temperature. This green protocol has also been successfully extended to the regioselective synthesis of 3-substituted indoles via indole and nitroalkene by a free radical pathway.

β-Cyclodextrin: A Biomimetic Catalyst used for the Synthesis of 4H-chromene-3-carbonitrile and Tetrahydro-1H-xanthen-1-one Derivatives

An efficient and facile protocol has been documented for the synthesis of 4H-chromene and xanthen-1-one derivatives via a three component one pot reaction of salicyladehyde, malononitrile/dimedone and indole utilizing biomimetic catalyst. Affiliation between biomimetic and organocatalyst exhibits a versatile and high catalytic activity emerging to be a sustainable alternative to other catalysts. The significant features of this protocol are compatibility with various types of indole and active-methylene compound, accomplishment of high yields, cleaner reaction condition and avoidance of the use of costly catalysts. Recyclability of β-cyclodextrin a “biomimetic catalyst” is a significant feature of this protocol.Graphical Abstract